Floor wave microphone stand

ABSTRACT

A microphone stand for responding to the floor wave of a distant acoustical source which utilizes a body of open cellular foam plastic having between 10 and 80 voids per linear inch and having a total volume of voids of at least 90 percent of the total volume of the body. The body has a flat side which permits it to be placed upon a horizontal surface such as a floor and a cavity therein to snugly accommodate a microphone and hold it in position.

States Patent [191 Burroughs FLOOR WAVE MICROPHONE STAND [75] Inventor:Louis Burroughs, Lake l-lavasu,

Ariz.

[73] Assignee: Electro-Voice, Incorporated,

Buchanan, Mich.

[22] Filed: May 29, 1973 [21] Appl. No.: 364,309

[52] US. Cl. 179/146 R, 179/184 [51] Int. Cl H04r 1/02 [58] Field ofSearch 179/146 R, 147, 184

[56] References Cited UNITED STATES PATENTS Gorike 179/184 Jan. 21, 1975Primary ExaminerWilliam C. Cooper [57] ABSTRACT A microphone stand forresponding to the floor wave of a distant acoustical source whichutilizes a body of open cellular foam plastic having between 10 and 80voids per linear inch and having a total volume of voids of at least 90percent of the total volume of the body. The body has a flat side whichpermits it to be placed upon a horizontal surface such as a floor and acavity therein to snugly accommodate a microphone and hold it inposition.

4 Claims, 4 Drawing Figures FLOOR WAVE MICROPHONE STAND The presentinvention relates generally to microphone stands, that is, supportstructures for mounting a microphone in position to respond toacoustical energy. More specifically, the present invention relates tomicrophone stands for use in positioning microphones for responding toacoustical energy originating at a substantial distance from themicrophone.

Microphone stands are well known in the art and generally consist of abase adapted to be positioned upon a horizontal surface, usually a flooror table, a stern extending from the base generally perpendicular to thehorizontal surface, and a clamping structure for securing the stem tothe microphone itself. Often the microphone is removable from the clamp,and often the stand includes a compliant structure between the stern andthe microphone for isolating the microphone from mechanical vibrationsderived from the base. In addition to the stationary stands of the typedescribed above, microphones are often mounted for movement on a boom,and such devices include a mechanical means for moving the clamp andmicrophone with respect to the base, and in some cases for moving thebase with respect to the horizontal surface.

Most microphone stands mount the microphone at a considerable distancefrom the horizontal surface, often four or five feet. Stands formounting a microphone on a table, however, may position the microphone afew inches above the surface of the table. The present inventor hasrecognized that such microphones may be positioned on the floor torespond to acoustical energy originating at a substantial distance, andthe microphone will respond primarily to the floor wave of thatacoustical energy.

Acoustical energy originating at a distance above the floor of a room,for example 3 feet, and at a substantial distance from the microphone,for example to feet, will produce reflections from the floor which arereceived by a microphone mounted above the floor level. Since soundwaves travel from the point of origin outwardly in all directions at auniform rate, those sound waves reaching the microphone after reflectionfrom the floor travel a further distance than the sound waves whichtravel directly from the source to the microphone. Accordingly, there isa phase difference between the sound wave which travels directly fromthe source to the microphone and the sound wave which is reflected fromthe floor to the microphone. Accordingly, the floor wave of theacoustical energy, that is, the acoustical energy from a distant sourcewhich may be detected at a few inches above the floor, contains thedirect wave from the sound source and only those waves which arereflected immediately in front of the microphone, and hence, the floorwave does not contain acoustical energy substantially out of phase withthe direct sound wave from the source. The Apr., 1971 issue of DBMagazine contains an article entitled A Distant Micing (sic) Techniqueby Anderson and Schuelin which describes a microphone stand designedspecifically for the purpose of positioning a microphone to respond tothe floor wave from a distant source.

While the acoustical conditions adjacent to the floor with respect to adistant source are different than the acoustical conditions at asignificant distance above the floor, it is also true that theenvironmental conditions at floor level differ from those above thefloor level. Depending upon the precise location, microphones mountedadjacent to the floor are subjected to larger quantities of dust, dirt,air drafts or winds, and are in closer proximity to shocks andvibrations transmitted from the floor. It is an object of the presentinvention to provide a microphone stand for positioning a microphoneadjacent to the floor to respond to the floor wave of a distant sourcewhich protects the microphone against dust, dirt, wind noises, andminimizes the effects of shock and vibration.

Further, it is an object of the present invention to provide amicrophone stand which will permit the microphone to be positioned veryclose to the floor and yet maintain shock and vibration isolation,protection against dust, dirt and wind noises.

In addition to these objects, it is an object of the present inventionto provide a very inexpensive and durable microphone stand, and amicrophone stand which may readily be removed from the microphone topermit the microphone to be used as ahand held microphone or mounted ona conventional stand.

The inventor has found that a microphone stand for responding to thefloor wave of a distant acoustical source and achieving the foregoingobjects may consist of a body of open cellular foam plastic with cellsizes sufficiently large to permit the passage of sound but ofinsufficient size to permit ready passage of dust and dirt, this bodyhaving a flat side which may be positioned on the floor and a cavitytherein for containing a microphone. The inventor has found that thecavity is preferably in the form of a recess from the flat side of thefoam body to permit ready installation and removal of the microphone.The foam plastic should be compliant to dampen shock and vibrationspresent on the floor structure.

The invention will be more thoroughly described with reference to theaccompanying drawings, in which:

FIG. 1 is an elongated sectional view of a microphone stand constructedaccording to the present invention including a microphone mountedtherein;

FIG. 2 is a bottom view of the microphone stand of FIG. 1, themicrophone having been removed;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2; and

FIG. 4 is a side elevational view of the microphone stand of FIGS. 1through 3.

FIG. 1 shows a microphone 10 mounted within a body of foam plastic 12which constitutes the microphone stand. The body l2 has a flat surface14 which is adapted to be positioned on a floor, or may be positioned ona table if desired. The body has an axis disposed in the surface 14parallel to the axis of elongation of the body 12, this axis beinglocated at 16 in' FIGS. 2 and 3, and the body 12 is semi-cylindricalwith respect to the axis 16. The body 12 has a forward end 18 and arearward end 20, and these ends are quarter spheres .with respect tocenters located in the flat surface 14 at the points 22 and 24illustrated in FIG. 2. The radius of curvature of the quarter sphericalends 18 and 20 is the same as the radius of the semicylindrical portionof the body 12. I

A circular recess 26 extends into the body 12 concentrically about anaxis normal to the surface 14 at the center 16 of the quarter sphericalend 18 of the body. The recess terminates in a semi-spherical dome 28with a center 30, as illustrated in FIG. 3. The center 30 is located onthe axis of the recess 26 and spaced from the center 16 on the flatsurface 14 by a distance equal to the radius of the semi-spherical dome28, thereby establishing the position of the microphone within the body12 as will be hereinafter further explained. A cylindrical channel 32extends parallel to the axis 16 from the recess 26 to an opening 34 inthe quarter spherical end 20 of the body 12, the axis of the channel 32passing through the center 30 of the semi-spherical dome 28.

The body 12 has been shaped to accommodate the microphone which has acylindrical shank 36 with a diameter approximately equal to the diameterof the channel 34. The microphone 10 also has a generally spherical head38 with a radius slightly less than the radius of the semi-sphericaldome 28. The microphone is an omnidirectional microphone as illustratedbut may also be a directional microphone since all portions of themicrophone are subjected to the sound field through the foam body 12.Further, the microphone has a connector 40 disposed at its end oppositethe head, and the connector 40 is removably connected to a cable 42.

The connector 40 and cable 42 are first disengaged to position themicrophone 10 within the body 12. The cylindrical shank 36 of themicrophone is then inserted into the channel 32 of the foam body 12through the recess 26. The body 12 is constructed of sufficientlyresilient material to permit the forward end 18 of the body to bedistorted, and thus permit the cylindrical shank 36 of the microphone tobe translated in the cylindrical channel 32 until the spherical head 38of the microphone comes into abutment with the wall of the recess 26.The resilency of the material of the body 12 will thus permit the end 18to resume its normal position, and the microphone will be positionedwithin the body as shown in FIG. 1. The cable 42 may then simply beaffixed to the connector 40 of the microphone, the connector 40protruding from the end of the body to permit connection.

The body 12 should be constructed of open cellular resilient foamplastic, and the cells should be sufficiently open to freely pass soundwaves. It will be noted that the distance between the adjacent exteriorsurface of the body 12 and the spherical dome 28 is significantly lessthan the distance between other portions of the recess 26 and theexterior surface of the body 12 and may be as little as one-sixteenthinch, but no portion of the acoustical path to the head of themicrophone should exceed 6 inches. This can only be accomplished withoutimpairing the acoustical performance of the microphone by virtue of thefact that the open cellular foam material of the body is substantiallytransparent with respect to sound waves and does not provide asignificant impedance to the passage of sound waves. In the particularembodiment described, the distance between the center of thesemi-spherical dome 28 and the adjacent surface of the body 12 isapproximately one-fourth inch, and this has been found to besatisfactory to protect the microphone against dirt and dust and to forman effective wind screen.

The open cellular foam material of the body may be the same typematerial utilized in wind screens, such as that disclosed in U.S. Pat.No. 3,236,328 of the present inventor entitled ACOUSTICAL DEVICE WITHPROTECTIVE SCREEN. The open foam cellular material should have between10 and 80 cells per linear inch and at least 90 percent of the volume ofthe body 12 should constitute voids. Polyurethane foam has been found tomeet these requirements.

The cylindrical head 38 of the microphone I0 is positioned as close tothe flat surface 14 as possible without permitting the head 38 tocontact the horizontal floor or other surface upon which the flatsurface 14 of the body 12 rests. In the particular constructiondescribed, the head 38 of the microphone is spaced from the surface 14by a distance of approximately one-fourth inch. Substantially allreflections from the floor resulting from a distant source of acousticalenergy will arrive in phase with the acoustical energy arriving on adirect line from the source. However, the fact that reflections from thefloor occuring near the microphone do arrive at the microphone, therewill be a gain in microphone output up to about 6 decibels over theoutput of the microphone at a significant elevation from the floor.

The recess 26 and channel 32 are fabricated to accommodate theparticular microphone 10 described in this embodiment. Other shapedrecesses and channels may also be employed in the body 12 to accommodatedifferent shaped microphones. Further, the exterior shape of themicrophone may be varied, but it is desirable to provide at leastthree-eighths inch of foam plastic between those portions of themicrophone that bear the weight of the microphone and the flat surface14 for purposes of damping vibrations and shock.

The scope of the present invention is set forth in the accompanyingclaims, rather than the foregoing specification.

The invention claimed is:

l. A microphone and stand assembly comprising a body of open cellularfoam plastic having between 10 and voids per linear inch and at leastpercent of its volume in voids, one side of said body being flat andadapted to rest upon a flat surface, said flat side having a recessextending therein, said recess terminating at a distance no less thanone-sixteenth inch from the adjacent surface of the body, and amicrophone disposed within the recess and supported by the body, themicrophone being spaced from the plane of the flat surface of the body.

2. A microphone and stand assembly comprising the combination of claim 1wherein the foam plastic of the body has a compliance at least equal topolyurethane.

3. A microphone and stand assembly comprising the combination of claim 1wherein the microphone has a generally spherical head at one end and anelongated cylindrical shank extending therefrom, and the body has asemi-cylindrical portion centered on an axis disposed on the flat sideof the body and quarter-spherical ends at opposite ends of the axis of asemi-cylindrical portion, said quarter-spherical end portions beingcentered on the axis of the semi-cylindrical portion, the recess beingcylindrical with an axis passing through the center of the halfspherical surface at one end of the body normal to the flat surface,said recess having a semi-spherical dome centered on the axis of therecess at a distance from the flat surface approximately equal to theradius of the half spherical dome, the channel extending from the recessparallel to the flat surface in alignment with the center of thesemi-spherical dome, the shank of the microphone being snugly disposedin the channel and supporting the microphone within the body.

tance no less than one-sixteenth inch from the adjacent surface of thebody, said cavity being adapted to accommodate the microphone and snuglyfit at least a portion of the microphone to mount the microphone in afixed position with respect to the body.

1. A microphone and stand assembly comprising a body of open cellularfoam plastic having between 10 and 80 voids per linear inch and at least90 percent of its volume in voids, one side of said body being flat andadapted to rest upon a flat surface, said flat side having a recessextending therein, said recess terminating at a distance no less thanone-sixteenth inch from the adjacent surface of the body, and amicrophone disposed within the recess and supported by the body, themicrophone being spaced from the plane of the flat surface of the body.2. A microphone and stand assembly comprising the combination of claim 1wherein the foam plastic of the body has a compliance at least equal topolyurethane.
 3. A microphone and stand assembly comprising thecombination of claim 1 wherein the microphone has a generally sphericalhead at one end and an elongated cylindrical shank extending therefrom,and the body has a semi-cylindrical portion centered on an axis disposedon the flat side of the body and quarter-spherical ends at opposite endsof the axis of a semi-cylindrical portion, said quarter-spherical endportions being centered on the axis of the semi-cylindrical portion, therecess being cylindrical with an axis passing through the center of thehalf spherical surface at one end of the body normal to the flatsurface, said recess having a semi-spherical dome centered on the axisof the recess at a distance from the flat surface approximately equal tothe radius of the half spherical dome, the channel extending from therecess parallel to the flat surface in alignment with the center of thesemi-spherical dome, the shank of the microphone being snugly disposedin the channel and supporting the microphone within the body.
 4. A standadapted to support and accommodate a microphone comprising a body ofopen cellular foam plastic having between 10 and 80 voids per linearinch and at least 90 percent voids in the volume thereof, one side ofsaid body being flat and adapted to rest upon a flat surface, a cavityin said body terminating at a distance no less than one-sixteenth inchfrom the adjacent surface of the body, said cavity being adapted toaccommodate the microphone and snugly fit at least a portion of themicrophone to mount the microphone in a fixed position with respect tothe body.